Linear motion motor with rectangular coil construction

ABSTRACT

A linear motion motor includes a reciprocatable armature carried by a stator comprising a plate with four parallel non-magnetic rods. A rectangular coil is wound on the rods and is supported thereby only at inside corners of the coil. The stator includes a permanent bar magnet secured at one end to one end wall of a Ushaped magnetic frame. The other end of the bar magnet is formed with a rectangular pole piece disposed inside a rectangular hole in the other end wall of the frame. The coil extends longitudinally between the air gap defined between the edges of the pole piece and hole in the other end wall. The rods are slidably engaged in corner notches formed in the pole piece.

United States Patent Lathrop [54] LINEAR MOTION MOTOR WITH RECTANGULARCOIL CONSTRUCTION [72] Inventor: Raymond Lathrop, Canoga Park, Calif.

[73] Assignee: Vernitron Corporation, Great Neck, NY.

[22] Filed: Sept. 28, 1970 [21] Appl. No.: 75,861

521 vs. Cl ..310/13, 310/27 [51] Int.Cl. ..H02k41/00 [58] FieldofSearch..3l0/12-l4, 27,

[56] References Cited UNITED STATES PATENTS 3,161,793 11/1971 Laithwaite..310/27 3,505,544 4/1970 Helms ..310/14 2,846,520 8/1958 Browncombe179/115.5

2,842,688 7/1958 Martin ..310/27 2,636,139 4/1953 Winget ..310/123,067,404 12/1962 Hildebrandt ..3l0/27 3,106,653 10/1963 Fowler..l79/115.5

OTHER PUBLICATIONS IBM Tech. Dicl. Bulletin, page 2,273, Vol. 12, No.12, May 1970, High Force Const. Voice Coil Motor...," Rexford PrimaryE.\'aminer.l. D. Miller Assistant Examiner-R. Skudy Attorney-Edward H.Loveman 5 7] ABSTRACT A linear motion motor includes a reciprocatablearmature carried by a stator comprising a plate with four parallelnon-magnetic rods. A rectangular coil is wound on the rods and issupported thereby only at inside corners of the coil. The statorincludes a permanent bar magnet secured at one end to one end wall of aU-shaped magnetic frame. The other end of the bar magnet is formed witha rectangular pole piece disposed inside a rectangular hole in the otherend wall of the frame. The coil extends longitudinally between the airgap defined between the edges of the pole piece and hole in the otherend wall. The rods are slidably engaged in corner notches formed in thepole piece.

4 Claims, 6 Drawing Figures PATENTEDAFRZSIQYE 3,659,124

SHEET 1 UF 2 INVENTOR. RAYMOND LATHROP F164 5 Mg ATTORNEY PATENTEDAPR 25I972 SHEET 2 CF INVENTOR. RAYMOND LATHROP ATTORNEY LINEAR MOTION MOTORWITH RECTANGULAR COIL CONSTRUCTION This invention concerns a linearmotion motor having a permanent magnet stator and more specifically witha linear motion motor having a permanent magnet stator and areciprocating armature with a rectangular coil.

l-leretofore linear motion motors have generally employed statorsprovided with cylindrical coils, and an axially reciprocating permanentmagnet armature. The prior construction has a number of disadvantagessuch as excessively large air gaps which reduce the maximum flux densityand force producing capability; excessive eddy currents which causepower losses during periods of motion; excessive heating due to theround coil structure encircling the armature, limited coil length due tocylindrical configuration of the stator and consequent reduction inforce per unit of current drawn and power consumed, complex structure,high manufacturing cost, etc.

The present invention is directed at overcoming the above and otherdifficulties and disadvantages of prior linear motion motors, and inaddition providing a linear motion motor with improved performance for agiven size with reduced power consumption. According to the inventionthere is provided a linear motion motor, based on the principle ofproducing a linear force or torque by interaction between a permanentmagnet and a coil carrying a unidirectional current (D.C.). The forceproduced is directly proportional to the product of the magnetic fluxdensity and the magnitude of current carried by the coil. Since themagnetic flux density is unidirectional and of constant value, thedirection of force is determined by the directional sense or polarity ofthe current in the coil.

The device embodying the invention employs astator frame which isrectangularly U-shaped, with a rectangular permanent magnet coreextending from one end of the frame to a rectangular hole in the otherend of the frame. A pole piece as defined by a flange on the free end ofthe core is formed with curved corner notches. The armature comprises arectangular apertured end plate carrying at its corners four cylindricalnon-magnetic rods which are slidably engaged in the corner notches ofthe pole piece. A shaft or other driven load may be attached to the endplate of the armature. Wound on the nonmagnetic rods is a rectangular,helical coil to the terminals of which is applied a D. C. current. Whenthe electric current flows in one direction the armature moves axiallyoutward of the stator frame. When the current flow is reversed thearmature moves inwardly of the stator frame.

The principal object of the present invention is to provide a linearmotion of improved performance and reduced power consumption.

Another object of the present invention is to provide a linear motionmotor having a rectangular coil supported only at its corners.

Another object of the present invention is to provide a linear motionmotor having a rectangular core supported at its corners therebyresulting in a maximum flux density for a given size and magnetstructure.

A still further object is to provide an improved linear motion motorhaving an improved force per ampere of current drawn, minimal powerconsumption and a large overall efficiency of operation.

These and other objects and many of the attendant advantages of thisinvention will be readily appreciated as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings in which:

FIG. I is a side view of a linear motion motor embodying the instantinvention;

FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 1;

FIG. 4 is a cross sectional view taken alongline 4--4 of FIG. 1;

FIG. 5 is a longitudinal sectional view taken along line 5-5 of FIG. 1;and

FIG. 6 is an exploded perspective view of the pans of the motor of FIGS.1-5.

Referring now to the drawings wherein like reference charactersdesignate like or corresponding parts throughout, there is illustratedin FIG. 1-6 a linear motion motor generally designated by referencenumeral. I0 having a stator 11 and an armature 12. The stator comprisesa rectangular U-shaped frame 15 made of magnetic material such as softiron or the like. The frame has parallel rectangular or square endplates or walls 14, 16 integral with a flat rectangular base plate orwall 18. End plate or wall 16 is formed with a rectangular hole 20 inwhich is set one end 21 (FIG. 5) of a rectangular bar magnet 19 whichserves as a core 22 for the stator. The core 22 is formed with arectangular pole piece 24 at its opposite end and comprises a flangewhich extends radially outward of the core 22. The pole piece 24 isdisposed within a rectangular or square hole 23 formed in the end wallor plate 14 of the stator frame. The end walls 14, 16 and base plate 18serve as a magnetic flux return path cooperating with the pole piece 24.The corners of the pole piece 24 are formed with concave, quartercylindrical notches 26 and each of the four edges 28 are spaced from aninner edge 30 of the end wall 14. The pole piece 24 is coplanar with thewall 14 to define a narrow rectangular passage G all around the polepiece 24. The N and S poles of the core 22 are at opposite ends of thebar magnet 19. By the arrangement described, a permanent magneticcircuit is maintained between the ends of core 22 via frame 15 and thepassage G between the pole pieces 14, 24.

The reciprocating armature 12 is comprised of a rectangular or squareend plate 35 which is slightly larger than hole 23. At corners of theplate 35 are holes 36 into which are secured by any conventional meansthe ends of four non-magnetic rods 38 which extend perpendicular toplate 35. The rods 38 are parallel to each other and of equal length.Inner sides of the rods are slidably engaged in the curved notches 26 atthe corners of the pole piece 24 and form part of the magnetic circuitbetween pole piece 24 and wall 14. Wound on the rods for substantiallytheir entire length is an insulated wire coil 40. This coil isrectangular in cross section as clearly shown in FIGS. 3, 4, and 6. Theair gap G, defined between the coil 40 and the edge of the pole piece 24is very minute, being just sufficient to permit free longitudinalreciprocating movement of the armature in the stator. This minimal airgap optimizes the magnetic flux density, and improves torque and overallefficiency. Holes 42 are provided in plate 35 to vertilate the interiorof the armature, and thus minimize the working temperature of theassembly, and to minimize the mass of the armature.

Threaded holes 44 are provided in the plate 35 to receive screws 46 bymeans of which a driven shaft 48 having a pair of apertured spider arms50 may be attached to the armature 12 for reciprocating movementtherewith and to maintain the air gap G. A unidirectional current may beapplied to ends or terminals 41 of coil 40. In one direction of currentflow the armature will move axially outward of the stator. Reversing thedirection of current flow will reverse the direction of movement of thearmature longitudinally of the stator.

The device is characterized by relative simplicity of construction,rugged structure, economy in manufacture, reliability in operation,improved operating efficiency, ease of assembly, etc.

It should be understood that the aforegoing relates to only a preferredembodiment of .the invention, and that it is intended to cover allchanges and modifications of the example of the invention herein chosenfor the purposes of the disclosure, which do not constitute departuresfrom the spirit and scope of theinvention.

The invention claimed is:

1. A linear motion motor comprising a stator having a rectangularU-shaped magnetic frame with .parallel-endwalls, a first one of saidwalls having a rectangular hole therein to define a first pole piece, apermanent bar magnet secured at one end to the second of said end wallsand extending perpendicuarly thereto toward said first end wall, saidbar magnet terminating in a rectangular second pole piece disposedinside said hole coplanar 5 with said first end wall, said second polepiece being peripherally spaced from said hole to define a rectangularair gap thereat,

a reciprocal armature supported by said stator, said armature comprisinga rectangular helical coil insulated wire extending longitudinallythrough said air gap to enclose said bar magnet and said second polepiece; and

a coil support means comprising a flat rectangular shaped plate and fourrods secured at one end thereof near each of the corners of said plateand extending parallel to each other and perpendicular to said plate,said coil being wound on said rods and wherein said second pole piecehas corner notches formed therein, said rods being respectively slidablyengaged in said notches.

2. A linear motion motor as defined in claim 1, further comprising adriven member attached to said plate and reciprocatable with saidarmature.

3. A linear motion motor as defined in claim 1, wherein said coil hasend terminals to which a reversible direct current source may beconnected, so that said armature moves axially in one direction bymagnetic interaction with the magnet when the current flows in onedirection, and said armature moves axially in an opposite direction whenthe current flow is reversed.

4. A linear motion motor as defined in claim 2, wherein said platesupporting said coil is slightly larger than said hole in said end wallto serve as an abutment limiting inward movement of said armature intosaid stator, said plate having holes for ventilating the interior ofsaid coil and, attaching said driven member to said armature, therebyminimizing the mass of said armature.

' it s a i

1. A linear motion motor comprising a stator having a rectangular U-shaped magnetic frame with parallel end walls, a first one of said walls having a rectangular hole therein to define a first pole piece, a permanent bar magnet secured at one end to the second of said end walls and extending perpendicuarly thereto toward said first end wall, said bar magnet terminating in a rectangular second pole piece disposed inside said hole coplanar with said first end wall, said second pole piece being peripherally spaced from said hole to define a rectangular air gap thereat, a reciprocal armature supported by said stator, said armature comprising a rectangular helical coil insulated wire extending longitudinally through said air gap to enclose said bar magnet and said second pole piece; and a coil support means comprising a flat rectangular shaped plate and four rods secured at one end thereof near each of the corners of said plate and extending parallel to each other and perpendicular to said plate, said coil being wound on said rods and wherein said second pole piece has corner notches formed therein, said rods being respectively slidably engaged in said notches.
 2. A linear motion motor as defined in claim 1, further comprising a driven member attached to said plate and reciprocatable with said armature.
 3. A linear motion motor as defined in claim 1, wherein said coil has end terminals to which a reversible direct current source may be connected, so that said armature moves axially in one direction by magnetic interaction with the magnet when the current flows in one direction, and said armature moves axially in an opposite direction when the current flow is reversed.
 4. A linear motion motor as defined in claim 2, wherein said plate supporting said coil is slightly larger than said hole in said end wall to serve as an abutment limiting inward movement of said armature into said stator, said plate having holes for ventilating the interior of said coil and, attaching said driven member to said armature, thereby minimizing the mass of said armature. 